Conventionally, a collision of a walker, a pedestrian or the like with a vehicle is detected by a device that is disclosed, for example, in Japanese patent document JP-A-2006-117157 (Also published as US patent document 20060087417). This obstacle detection device for vehicular use in the above disclosure includes an absorber, a pressure sensor, a speed sensor, and an airbag ECU device. The absorber absorbs an impact of the collision that is caused by a collision of an object with the vehicle. The absorber includes a chamber member and a connection member. The chamber member is connected by using the connection member, and is fixed on a front face of a bumper reinforcement. The inside of the chamber member, that is, a chamber, is filled with air. The pressure sensor is a sensor for detecting a pressure in the chamber. The pressure sensor is connected to the connection member through a tube. The speed sensor for detecting a vehicle speed is disposed in a vehicle. The pressure sensor and the speed sensor are connected to the airbag ECU. The airbag ECU determines whether the colliding object that collides with the bumper of the vehicle is a walker based on a detection result of the pressure sensor and the speed sensor. More practically, whether the pressure inside the chamber exceeds a threshold that is determined based on the vehicle speed is used as a criterion for determination that the colliding object is a walker.
The chamber member and the absorber in the obstacle detection device are, in some cases, disposed as separate members for more securely absorbing the impact of the collision with the colliding object. For example, the absorber is disposed to cover the chamber member. In this case, the absorber is deformed as the vehicle collides with the object. In the course of collision, the chamber member may be bound by the deformed absorber. If the chamber member is bound by the absorber, the load for deformation may increase, and the deformation of the chamber member may be interfered. Therefore, the pressure in the chamber member may be prevented from being changed, thereby leading to an inaccurate detection of the collision of the vehicle with an object.